Mobile data and voice communication continues to evidence significant growth. With increasing popularity of data and voice communication, it is more likely that the communication needs of a large number of users must to be met which are all located within a small area, a case referred to as dense crowd scenario in the art. Typical examples include sport arenas or large office buildings.
In order to increase data transmission performance and reliability, the so-called multiple input and multiple-output (MIMO) technology may be used in wireless radio telecommunication for transmitting information between a base station and terminals of users. MIMO systems may use multiple send and receive antennas for wireless communication at a base station. The MIMO technology forms the basis for coding techniques which use the temporal as well as the spatial dimension for transmitting information. The enhanced coding provided in MIMO systems allows a quality and data rate of the wireless communication to be increased.
In a massive MIMO system, the base station may include a large number of antennas, e.g. several tens or even in excess of one hundred antennas with associated transceiver circuitry. The extra antennas of the MIMO base station allow radio energy to be spatially focused which improves capacity and radiated energy efficiency. Space diversity multiple access (SDMA) is used in a massive MIMO system to keep interference low for the various terminals in the cell.
When several terminals connected to the same base station are located close to each other, the SDMA may not allow the base station to distinguish signals received from the several terminals and/or the base station may not be able to rely on SDMA to focus radio energy at a desired one of the several terminals. More than one terminal may be located in the spatial region in which the radio energy is focused by the base station. Massive MIMO systems may be deployed in buildings such as office buildings, shopping malls and so on, sport arenas or other areas in which a large density of users can occur and terminals are likely to be located close to each other. The spatial resolution which can be attained may also depend on the environment. For a rich scattered environment, the spatial resolution may in general be better. However, when terminals are very close to each other or the environment is such that the base station cannot distinguish two or more devices due to its spatial resolution, interference may increase even when SDMA is used in a cellular MIMO system.